Rotary internal combustion engines having peripheral seals, such as apex seals in Wankel engines, usually require oil injection to these seals to prevent excessive wear and loss of performance. Typically, such engines use a mechanical oil pump which driven by the rotatable shaft of the engine to deliver the oil to the seals through suitable fluid conduits communicating with the pump and with the environment of the seals; this pump is provided in addition to the main oil pump providing the oil circulation to other systems of the engine (e.g. bearing lubrication, rotor cooling). However, engine driven mechanical pumps have limited flexibility as to the frequency of injection, which is usually fixed for a given engine speed. Accordingly, the frequency of oil delivery to the seals may be difficult or impossible to adjust and tailor to specific operating conditions, particularly without a change in the quantity of oil being injected.